Temperature Converter
Convert temperature between Celsius, Fahrenheit, Kelvin, and Rankine. Instant temperature conversion with formula explanation.
About this calculator
Type a temperature into any of the four boxes, Celsius, Fahrenheit, Kelvin or Rankine, and the other three update as you type. A short note appears for landmark values such as freezing, body temperature and boiling.
The formulas include the offsets that make temperature different from other units, so results are right at negative values too. Use it for weather abroad, oven settings, science homework or checking a thermometer.
How to use it
- Type a value in any box: Celsius, Fahrenheit, Kelvin or Rankine.
- The other three fill in automatically, to four decimals.
- Read the note below for landmark temperatures.
Formulas
°F = °C × 9/5 + 32, °C = (°F − 32) × 5/9, K = °C + 273.15 and °R = (°C + 273.15) × 9/5 = °F + 459.67. Temperature scales have different zero points, so unlike length you cannot just multiply. The two scales agree at −40, where −40 °C equals −40 °F.
Worked example
Reference points
| Water freezes | 0 °C = 32 °F = 273.15 K |
| Body temperature | 37 °C = 98.6 °F = 310.15 K |
| Water boils (sea level) | 100 °C = 212 °F = 373.15 K |
| Moderate oven | 180 °C = 356 °F |
| Absolute zero | −273.15 °C = −459.67 °F = 0 K |
Tips and common mistakes
- Quick estimate from °C to °F: double it and add 30. It is close within the normal range.
- Oven recipes: 180 °C is about 350 °F, 200 °C about 400 °F.
- Kelvin has no degree symbol and never goes below zero.
- Fever in an adult starts around 38 °C (100.4 °F).
- Use the −40 crossover to sanity-check: both scales read the same.
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 and add 32.
How do I convert Fahrenheit to Celsius?
Subtract 32 and multiply by 5/9.
What is 37 °C in Fahrenheit?
98.6 °F.
What is absolute zero?
0 K, or −273.15 °C, the lowest possible temperature.
At what temperature are Celsius and Fahrenheit equal?
−40.
What is Rankine?
An absolute scale that uses Fahrenheit-sized degrees, with 0 °R at absolute zero.